The fifth generation mobile communication standard of mobile phone, also known as the fifth generation mobile communication technology, abbreviated to 5G. It is also an extension of 4G under study. The network speed thereof is up to 5M/S-6M/S. 5G mainly covers mobile communications, Wi-Fi, high-speed wireless data transmission and other fields. In terms of user experiences, 5G has a higher rate and a wider bandwidth. The network speed of 5G is expected to be improved to about 10 times as that of 4G. A high-definition movie can be downloaded in only a few seconds. Consumer demands of virtual reality, ultra HD video and other higher requirements of network experience can be satisfied. In terms of industrial applications, 5G has higher reliability and lower time delay and can meet the specific needs of industrial applications such as intelligent manufacturing and automatic driving, broadening the space for the development of integrated industries, and supporting the innovation and development of the economic society. Therefore, compared to 4G, 5G requires a faster transmission rate, a lower transmission time-delay, and a higher reliability. Thus, the requirements of the 5G communication circuit board are higher transmission speed, lower transmission time delay, and better reliability.
The signal transmission speed relates to the materials. The scientific practice has proved that among the commonly used, conductor materials for circuit boards, the materials with the best current transmission performance are sequentially listed as gold, aluminum, and copper. Therefore, in order to satisfy the transmission requirements, the gold-plating etching process for the entire circuit board is the preferred requirement to meet the 5G technology.
In the requirements of the traditional gold-plating process, the gold-plating process generally uses the wire to plate. Terminal customers do not allow the use of gold-plated wire in the production of circuit boards during the gold-plated process, thus, causing many technical problems in the production.
In the traditional gold-plating etching process, the gold-plated area is higher than the non-gold-plated area, meaning that they are not in the same plane. While the traditional outer dry film etching process is used, the dry film cannot completely fill the connection between the gold-plated area and the non-gold-plated area due to the altitude difference. The etching solution infiltrates into the junction of gold and copper along the gap between gold and copper during the etching, which results in the etching gap and open circuit. Thus, it is a technical problem of gold-plating technology. In addition, in the traditional process, the etching of circuit, after gold-plating, is performed with acidic etching. The costs of outer film pressing, exposure, development, etching should also be taken into consideration, affecting the transmission rate and reliability of 5G signal board.